Could it be stomach flu -- or something else?

Q> I'm going on my first cruise, and I was concerned that I might get stomach flu. What should I do?

Fred Cicetti

Q. I'm going on my first cruise, and I was concerned that I might get stomach flu. What should I do?

A. Many seniors frequent cruise ships because vacationers can enjoy what is probably the most relaxing form of getaway. You travel with your own bedroom and all the amenities you can think of. But there are a lot of people on these floating paradises; that means lots of germs are along for the ride.

Among the most common germs are the ones that give you norovirus, also known as Norwalk Virus. This nasty bug gives you gastroenteritis, mistakenly called “stomach flu.” Gastroenteritis is an inflammation of the stomach and intestines; it is not related to flu, a respiratory illness caused by influenza virus.

Noroviruses are highly contagious. Usually they are found in contaminated food or drinks, but they also live on surfaces. They can be spread through contact with an infected person.

Noroviruses are the most common cause of gastroenteritis in the United States. Each year in the United States alone, 23 million norovirus infections cause about 50,000 hospitalizations and 310 deaths, according to the Centers for Disease Control and Prevention.

Norovirus (the common term for the infection) spreads swiftly wherever there are crowds of people – nursing homes, dormitories, hotels and cruise ships. (An outbreak recently shut down the Mohonk Mountain House for a week.)

Norovirus has become associated with cruises because health officials are required to track illnesses on ships, not hotels and other land-based facilities. Outbreaks on cruise ships are found and reported more quickly than those on land and make a lot of news.

Before we go further, let's discuss the nature of germs, which are defined as microbes that cause disease.

Microbes are microscopic organisms that are everywhere. Some microbes cause disease.

Others are essential for health. Most microbes belong to one of four major groups: bacteria, viruses, fungi or protozoa.

Bacteria are made up of only one cell. Less than one percent of them cause diseases in humans.

Harmless bacteria live in human intestines, where they help to digest food. Foods such as yogurt and cheese are made using bacteria.

Some bacteria produce dangerous poisons. Botulism, a severe form of food poisoning, is caused by toxins from bacteria. However, several vaccines are made from bacterial toxins.

Viruses are among the smallest microbes. They consist of one or more molecules that contain the virus's genes surrounded by a protein coat. Most viruses cause disease. They invade normal cells then multiply.

There are millions of types of fungi. The most familiar ones are mushrooms, yeast, mold and mildew. Some live in the human body, usually without causing illness. In fact, only about half of all types of fungi cause disease in humans. Penicillin and other antibiotics, which kill harmful bacteria in our bodies, are made from fungi.

Protozoa are a group of microscopic one-celled animals. In humans, protozoa usually cause disease. Some protozoa, like plankton, are food for marine animals. Malaria is caused by a protozoan parasite.

You can get infected by germs from other people in many different ways, including transmission through the air from coughing or sneezing, direct contact such as kissing or sexual intercourse, and touching infectious material on a doorknob, telephone, automated teller machine or a diaper.

Email questions to freelance health-care writer Fred Cicetti at fred@healthygeezer.com. Cicetti's book, “How to Be a Healthy Geezer,” is available for purchase at healthygeezer.com.